People who use their smart phones a lot - and who doesn't these days - may have poorer fitness levels as a result, a new study has found.

According to US researchers, people are now able to access a range of sedentary activities, such as surfing the internet and playing video games, more easily on their phones. As a result, they decided to look at the relationship between smartphones and physical activity levels.

They assessed over 300 college students. All were questioned about their phone use and physical activity levels, while almost 50 also had their fitness levels and body composition tested.

The study found that some participants spent up to 14 hours a day on their phones. Furthermore, those who spent a lot of time on their phones were less physically fit than those who spent no more than 90 minutes per day on them.

One participant said that it ‘definitely decreases my physical activity because if I'm bored, I can just download whatever I want'.

This is believed to be the first study to assess the link between mobile phone use and fitness levels. According to the researchers from Kent State University, despite the fact that phones are small and mobile, making it possible to use them while actually doing physical activity, many people are becoming more sedentary as a result of them.

Details of these findings are published in the International Journal of Behavioral Nutrition and Physical Activity.